Cards for Caravan Decks

A couple of friends and I have discovered an interest in actually playing Caravan, that sideshow game from New Vegas nobody ever learns the rules to. Deck construction allows multiple of an identical card (say, the King of Diamonds) as long as the backs are all suitably unique. To that end, I've cannibalized a couple of old playing card decks we used to take camping that have lost cards here and there, and weren't good for play anymore. We just put the cards in a shoebox organized by rank and then pull what we want to build decks. It's been fun so far.

The only problem is this is a rather small pile, especially if we want to do something silly like running 15 nines of spades, and we have almost no jokers. Rather than going out and buying a dozen brand new decks of cards for this purpose, since the low ranks probably won't see much use, is there a site somewhere where I could order individual cards from many different decks? Perhaps used casino decks? I know Ebay would have some used decks, and probably some rare or valuable promotional cards, but I figured I would ask about generic singles first.